The present invention relates to a magnetic disk drive, in particular, to a magnetic disk drive where a magnetic head supported by a carriage assembly is connected with a control section through a flexible printed circuit board, a head suspension assembly used in the magnetic disk drive, and a method of connecting a relay printed circuit board and a main printed circuit board.
In general, a magnetic disk drive comprises a magnetic disk arranged in a case, a spindle motor for supporting and rotating the magnetic disk, a carriage assembly for supporting a magnetic head, a voice coil motor for driving the carriage assembly, and a substrate unit.
The carriage assembly comprises a bearing portion mounted on the case, and a plurality of arms extending from the bearing portion, with a magnetic head attached to each of the arms via a suspension. The substrate unit has a main flexible printed circuit board (hereinafter referred to as a main FPC) extending to the vicinity of the bearing portion. Each of the magnetic heads is connected to one end of a relay flexible printed circuit board (hereinafter referred to as a relay FPC) provided on the arm, and the other end of the relay FPC is connected with the main FPC. Thus, each of the magnetic heads is electrically connected to the substrate unit via the relay FPC and the main FPC, to be controlled by the substrate unit.
In general, a flexible printed circuit board such as the main FPC and the relay FPC includes a base layer formed of an insulating material, a conductor pattern formed on the base layer and having a plurality of pads in a connecting portion, and a cover layer covering the entire conductor pattern excluding the pads.
A plurality of pads constituting a connecting portion are provided at the extended end of the main FPC, with each of the pads being plated with gold or solder. A plurality of pads constituting a connecting portion are provided at the other end of each of the relay FPCs, with a metallic bump being formed on each of the pads. Furthermore, a solder layer is formed on the bump.
When the connecting portion of the main FPC and the other end portion of the relay FPC are electrically connected, the other end portion of the relay FPC and the connecting portion of the main FPC are arranged facing to each other such that the pads of the main FPC and the bumps of the relay FPC oppose to one another. In this state, by heating the bumps and the solder layers on the pads from the base layer side of the relay FPC with a heating member such as a soldering iron, the solder layers are melted so that the pads provided in the connecting portion of the main FPC and the pads provided at the other end portion of the relay FPC can be electrically and mechanically connected with one another.
However, in the above-mentioned magnetic disk drive, since the heat for melting the solder layers is applied to the solder layers through the base layer of the relay FPC in connecting the main and relay FPCs, it is difficult to melt the solder layers quickly and sufficiently. Therefore, an oxide layer may be formed easily on the surface of the solder layer to deteriorate the connection reliability. Further, it is difficult to check the connecting state after soldering by the visual inspection, and thus it is difficult to guarantee the quality of the connecting portion to be a great obstacle in terms of maintaining the reliability.
The present invention has been contrived in consideration of the above-mentioned problems, and its object is to provide a magnetic disk drive capable of connecting a main flexible printed circuit board and a relay flexible printed circuit board easily and securely, allowing the visual inspection of a connecting portion, with a high connection reliability and a high quality, with a good assembling convenience, a head suspension assembly used in the magnetic disk drive, and a method of connecting a relay printed circuit board and a main printed circuit board to each other.
In order to achieve the above-mentioned object, a head suspension assembly used in a magnetic disk drive according to the present invention comprises a plate-like suspension having one end mounted with a magnetic head and the other end fixed to an arm; and a relay printed circuit board fixed on the suspension and the arm and having one end connected to the magnetic head and a connecting end portion extending to the arm.
The relay printed circuit board comprises a base layer, a conductor pattern formed on the base layer, a cover layer covering the conductor pattern, and a plurality of openings formed in the connecting end portion. The conductor pattern includes a plurality of electrode pads protruding into the openings, respectively.
A magnetic disk drive according to the present invention comprises a magnetic disk, a magnetic head for recording and reproducing information for the magnetic disk, a carriage assembly supporting the magnetic head to be movable with respect to the magnetic disk, a substrate unit for inputting/outputting signals for the magnetic head, a main printed circuit board extending from the substrate unit and having an extended end portion attached to the carriage assembly, and a relay printed circuit board provided on the carriage assembly, and having one end portion connected to the magnetic head, and a connecting end portion connected to the main printed circuit board.
The main printed circuit board comprises a base layer, a conductor pattern formed on the base layer, having a plurality of connecting pads provided in the extended end portion, a cover layer covering the conductor pattern excluding the pads, and a bump formed on each of the connecting pads by soldering;
The relay printed circuit board comprises a base layer, a conductor pattern formed on the base layer, a cover layer covering the conductor pattern, and a plurality of openings formed in the connecting portion so as to correspond to the pads of the main printed circuit board, wherein the conductor pattern comprises a plurality of electrode pads protruding to the inside of the openings.
The connecting end portion of the relay printed circuit board is arranged to oppose the extended end portion of the main printed circuit board such that the bumps of the main printed circuit board can contact with the respective electrode pads of the relay printed circuit board through the openings, and the electrode pads of the relay printed circuit board are soldered to the connecting pads of the main printed circuit board by heating and melting each of the bumps through the openings.
According to the magnetic disk drive having the above-mentioned construction, upon connecting the connecting end portion of the relay printed circuit board to the extended end portion of the main printed circuit board, the electrode pads and/or the bumps can be directly heated to melting the solder through the openings of the connecting end portion. At the same time, the connecting state can be observed visually through the openings.
In the above-mentioned magnetic disk drive, each electrode pad closes a part of the corresponding opening so that the heated and melted solder can flow on the side of the outer surface of the relay printed circuit board through the opening.
According to the construction, the heated and melted solder can reach the opposite side of the relay printed circuit board through the openings, thereby covering the entirety of the electrode pads.
Furthermore, according to a magnetic disk drive according to the present invention, each bump of the main printed circuit board has a height larger than the thickness of the connecting end portion of the relay printed circuit board before heating and melting the bump so that the bump protrudes from the outer surface of the relay printed circuit board on the opposite side with respect to the main printed circuit board as well as it pushes up the electrode pads in the direction projecting from the outer surface of the relay printed circuit board.
According to the magnetic disk drive of the above-mentioned construction, since the electrode pads project from the relay printed circuit board through the openings, a heat source can easily contact with the electrode pads, so that the connecting operation can be improved.
According to a magnetic disk drive according to the present invention, each bump of the main printed circuit board has a first bump made a conductive material having a melting point higher than that of the solder and formed on the connecting pad, and a second bump made of a solder and covering the first bump.
With the magnetic disk drive of the above-mentioned construction, since the first bump is provided, the height of the bump can be easily controlled even at the time of heating and melting of the solder so that the connecting position of the electrode pads can be controlled to be at a desired position.
A method of the present invention for connecting a connecting end portion of a relay printed circuit board and a extended end portion of a main printed circuit board, comprising the steps of:
preparing a main printed circuit board including a base layer, a conductor pattern formed on the base layer and having a plurality of connecting pads provided at the extended end portion, a cover layer covering the conductor pattern excluding the connecting pads, and a bump of solder formed on each of the connecting pads;
preparing a relay printed circuit board including a base layer, a conductor pattern formed on the base layer, a cover layer covering the conductor pattern, and a plurality of openings formed in the connecting end portion in correspondence with the connecting pads of the main printed circuit board, the conductor pattern having a plurality of electrode pads protruding into the openings, respectively;
opposing the connecting end portion of the relay printed circuit board to the extended end portion of the main printed circuit board such that the bumps of the main printed circuit board are in contact with the electrode pads of the relay printed circuit board through the openings, respectively; and
soldering the electrode pads of the relay printed circuit board to the connecting pads of the main printed circuit board by heating and melting the bumps through the openings, respectively.
Additional object and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The object and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.